During the welding process with laser-arc hybrid heat source, the energy matching of the laser and the arc is always the research hot spot of welding with hybrid heat source. The present research mainly focuses on the aspects of the high-power laser (2 kilowatts above) and arc hybrid welding mode and the welding technology as well as the welding performance of different materials, such as steel, aluminum. As disclosed in the China invention patent application ‘laser-arc hybrid pulse coordination control method’ (CN1418753A), under the condition of same pulse signal frequency, the laser peak power is triggered in the arc basic pulse region, while the laser basic pulse and the arc peak pulse are synchronous, so the stability of welding process can be improved obviously, so that the problems caused by the absorption and scattering effects to the laser by arc space plasma are solved, but this method only refers to the direct-current arc and especially high-power laser hybrid welding control. The research in domestic and abroad shows that a series of problems of the rigorous assembly gap requirement, low laser energy absorption ratio and the like caused by pure laser welding can be solved by adopting a laser and arc hybrid heat source welding technology, and at the same time, welding defects of splashing, cracking and the like can be reduced, the welding quality and efficiency can be improved effectively, so the laser-arc hybrid welding method has wide application prospects in the fields of aviation, ship building, automobiles and the like.
But, on one hand, high-power laser and arc hybrid mainly has the following problems:
Firstly, the electro-optic conversion efficiency of the present commercial laser device is low (less than 3%), and an output of 1 kilowatt laser requires about 35 kilowatts of electric energy [Graf T, Staufer H, Welding Journal, 2003, 82(1)], while the higher the output laser power is, the greater the energy loss is;
Meanwhile, the high-power laser device has a large volume, and high cost and maintaining expense (the cost of a 1 kilowatt laser device is about 100,000 Euro); and the research shows that the arc plays a role of defocus effect on the laser, which leads to the laser energy density reduction, and the higher the laser power is, the more obvious the defocus effect is by arc [CHEN Yanbin and other authors, welding journal, 2003, 24(3) by], so the hybrid of high-power laser and arc will lead to extreme energy consumption and high welding cost, which is not good for the practical production requirement.
On the other hand, when non-ferrous metal is welded, AC arc is selected generally. The oxide film on a welding plate is removed by utilizing the cathode atomizing effect of the AC arc. Because of the cyclic variation of AC arc current, when the laser pulse and the AC arc are matched, the laser pulse acts on different regions of the AC arc wave form, and different energy distribution modes can be generated, which plays different effects on the welding process and the results thereof, for instance, the dimension of weld penetration and the stability of arc in the welding process can be influenced directly. Thus, the optimization matching of pulse phases of the pulse laser and the AC arc is of great significance in improving the welding quality and efficiency with hybrid heat source.
People have paid high attention to the issue above, and begin to explore to perform hybrid welding by adopting the low-power laser and AC arc, and try to keep the advantages of the previous laser-arc hybrid welding technology, and simultaneously to achieve the aims of energy consumption reduction and cost conservation through reducing the laser power.